Vehicle underfloor structure

ABSTRACT

A vehicle underfloor structure includes a battery disposed under a floor of a vehicle and having at least one connector projecting from a front end of the battery, a suspension member provided adjacent to a vehicle front side of the battery, a lower end of the suspension member being located higher than a lower end of the battery, and a protector covering and protecting the at least one connector from below, the protector being laid between the battery and the suspension member.

CROSS REFERENCE TO RELATED APPLICATION

This application claims priority to Japanese Patent Application No.2018-157717 filed on Aug. 24, 2018, which is incorporated herein byreference in its entirety including the specification, claims, drawings,and abstract.

TECHNICAL FIELD

Disclosed herein is a vehicle underfloor structure in which a batteryand a suspension member are disposed under a floor of a vehicle.

BACKGROUND

A vehicle having a battery disposed under a floor of the vehicle hasbeen widely known hitherto. For example, WO 2014/045754 A discloses atechnique for disposing a battery under a floor of a vehicle. Accordingto WO 2014/045754 A, a plurality of connectors project from a front endof the battery.

However, according to WO 2014/045754 A, nothing is provided directlyunder the plurality of connectors, and accordingly terminals of theconnectors are exposed to the road surface. Therefore, while the vehicleis traveling, an object dropped on the road surface (hereinafter,referred to as an “on-road dropped object”) or a flipped stone may comeinto contact with the connectors to cause deterioration or damage of theconnectors.

Here, with a cross member extending in the vehicle width directionprovided in front of the battery and below the connectors, the on-roaddropped object collides with the cross member before colliding with theconnectors as the vehicle advances. Therefore, with provision of such across member, the contact between the connectors and the on-road droppedobject can be prevented to some extent. However, the cross memberlocated in front of the battery is often located above the lower ends ofthe connectors. Therefore, in the conventional vehicle, the connectorsprojecting from the front end of the battery cannot be properlyprotected.

Therefore, disclosed herein is a vehicle underfloor structure that canproperly protect the connectors projecting from the front end of thebattery.

SUMMARY

A vehicle underfloor structure disclosed herein includes a batterydisposed under a floor of a vehicle and having at least one connectorprojecting from a front end of the battery, a suspension member providedadjacent to a vehicle front side of the battery, a lower end of thesuspension member being located higher than a lower end of the battery,and a protector covering and protecting the at least one connector frombelow, the protector being laid between the battery and the suspensionmember.

This configuration causes the on-road dropped object to collide with theprotector before colliding with the connector as the vehicle advances.As a result, the connector can be effectively prevented from collidingwith the on-road dropped object, which in turn makes it possible toproperly protect the connector.

Further provided is an attachment bar attached to a lower portion of thesuspension member and extending in a vehicle width direction, and afront portion of the protector may be attached to the attachment bar.

This configuration causes many of the on-road dropped objects to collidewith the attachment bar before colliding with the protector. In otherwords, the likelihood of collision between the protector and the on-roaddropped object can be reduced, and the deformation and deterioration ofthe protector can be suppressed. Further, the attachment bar thusprovided allows the front end of the protector to be made low in height.As a result, the inclination angle of the protector can be made almostlevel. Even when the protector collides with the on-road dropped object,the collision angle can be small, so that deformation or damage of theprotector can be more effectively prevented.

In this configuration, the lower end of the attachment bar may belocated lower than the lower end of the at least one connector andhigher than the lower end of the battery.

Making the lower end of the attachment bar lower than the lower end ofthe connector makes it possible to effectively prevent the on-roaddropped object from colliding with the protector or the connector.Further, making the lower end of the attachment bar higher than thelower end of the battery makes it possible to prevent excessive loweringof the attachment bar and accordingly reduce the contact of theattachment bar with the road surface.

Further, at a rear portion of the suspension member, a rear cross partis provided, the rear cross part having an arch shape, extending in thevehicle width direction, and having a center in the vehicle widthdirection convex, and the attachment bar is attached to the rear crosspart to extend across the arch.

This configuration allows the rear cross part of the suspension memberhaving high rigidity to receive the force applied to the attachment barfrom the on-road dropped object.

The vehicle underfloor structure disclosed herein can properly protectthe connector projecting from the front end of the battery.

BRIEF DESCRIPTION OF DRAWINGS

Embodiment(s) of the present disclosure will be described by referenceto the following figures, wherein:

FIG. 1 is a plan view of a section around a battery;

FIG. 2 is a view seen from A of FIG. 1;

FIG. 3 is a perspective view of a protector;

FIG. 4 is an enlarged view of a D section of FIG. 3;

FIG. 5 is a cross-sectional view taken along B-B of FIG. 1;

FIG. 6 is a cross-sectional view taken along C-C of FIG. 1;

FIG. 7 is a partial perspective view of an attachment bar as seen frombelow;

FIG. 8 is a schematic side view of a section around the battery and arear cross part without the protector or the attachment bar,

FIG. 9 is a schematic side view of the section around the battery andthe rear cross part with the protector but without the attachment bar;

FIG. 10 is a schematic side view of the section around the battery andthe rear cross part with the protector and the attachment bar;

FIG. 11 is a schematic cross-sectional view of a section around afastening hole in a normal state; and

FIG. 12 is a schematic cross-sectional view of the section around thefastening hole in a front collision.

DESCRIPTION OF EMBODIMENTS

Hereinafter, the vehicle underfloor structure will be described withreference to the drawings. FIG. 1 is a plan view of a section around abattery 10. Further, FIG. 2 is a view seen from A of FIG. 1. Note that,in each of the drawings, “Fr,” “Up,” and “W” denote a vehicle frontdirection, a vehicle upper direction, and a vehicle width direction,respectively.

The vehicle is an electric vehicle equipped with at least a motor as apower source, and is, for example, an electric vehicle that travels onlyby power from the motor, or a hybrid vehicle that travels by power fromboth the motor and an engine. Under a floor panel of the vehicle, thebattery 10 that transfers electric power to and from a traveling motoris disposed. The battery 10 is a chargeable and dischargeable secondarybattery such as a lithium ion battery. The battery 10 has a battery case17 made of metal. Inside the battery case 17, a battery moduleconstituted by a plurality of battery elements (cells) connected inseries or in parallel is housed. In this example, the battery case 17has a substantially rectangular parallelepiped shape that is flat, andelongated in a vehicle longitudinal direction.

A connector 18 that connects the battery module and an external deviceis attached to a front surface of the battery case 17. For example, asignal line, a power line, and a refrigerant pipe are connected to theconnector 18. The number of connectors 18 may be appropriately changedas needed, and may be one, or two or more. In the drawings, an examplein which three connectors 18 are provided on the front surface of onebattery case 17 is illustrated.

A suspension member 12 is provided adjacent to a vehicle front side ofthe battery 10. The suspension member 12 is a frame member that supportsa suspension. The suspension member 12 of this example includes a frontcross part 20 and a rear cross part 22 that extend in the vehicle widthdirection, and a pair of side parts 24 that each connect an end of thefront cross part 20 and an end of the rear cross part 22, and has asubstantially square shape.

As is apparent from FIG. 2, the front cross part 20 has an inverted archshape whose center in the vehicle width direction is concave. Further,the rear cross part 22 has an arch shape whose center in the vehiclewidth direction is convex. A lower end of the suspension member 12 islocated higher than a lower end of the battery 10. Further, lower endsof some of the connectors 18 are located lower than the lower end of therear cross part 22 at positions identical to each other in the vehiclewidth direction.

A protector 14 is laid between the suspension member 12 and the battery10. FIG. 3 is a perspective view of the protector 14, and FIG. 4 is anenlarged view of a D section of FIG. 3. Note that, in FIG. 4, in orderto make a through-hole identifiable, sandy hatching is applied to theprotector 14.

The protector 14 covers the connectors 18 from below to protect theconnectors 18 from contact with a road surface or a flipped stone. Theprotector 14 is a plate member long in the vehicle longitudinaldirection and is, for example, a press-molded member. The protector 14has a plurality of raised parts 28 that are raised in a thicknessdirection and a plurality of recessed parts 26 that are recessed in thethickness direction. The raised parts 28 and the recessed parts 26 eachextend in the vehicle longitudinal direction. Further, the raised parts28 and the recessed parts 26 are alternately arranged. As is apparentfrom FIG. 3, neither a width of each of the raised parts 28 nor a widthof each of the recessed parts 26 is constant, and the width of theraised part 28 is slightly decreased toward a vehicle rear side.Further, the width of the recessed part 26 is significantly increasedtoward the vehicle rear side.

A front portion of the protector 14 is fastened to the rear cross part22 of the suspension member 12 using an attachment bar 16 (to bedescribed later). For this fastening, at around a front end of theprotector 14, a fastening hole 30 is formed through which a fasteningbolt 42 that is a fastening member is inserted. A diameter of thefastening hole 30 is larger than a major diameter of the fastening bolt42 and smaller than a diameter of a head of the fastening bolt 42. Thefastening bolt 42 inserted through the fastening hole 30 is screwed intoa weld nut 43 fixed to the attachment bar 16 to fasten the protector 14to the attachment bar 16. FIG. 5 is a cross-sectional view taken alongB-B of FIG. 1, showing how this fastening is performed.

The protector 14 further includes a cutout 32 that is located adjacentto a rear side of the fastening hole 30 and partially connected to thefastening hole 30 (see FIG. 4). The cutout 32 is sufficiently wider thanthe diameter of the head of the fastening bolt 42. The cutout 32 thusprovided allows the protector 14 and the attachment bar 16; that is, theprotector 14 and the suspension member 12, to easily disconnect fromeach other in a front collision. This will be described later.

Here, as shown in FIG. 4, a portion where the cutout 32 is formed isrecessed in a substantially V-shape. That is, the protector 14 includesa recess 34 constituted by a front slope surface 36 inclined to descendrearward and a rear slope surface 38 inclined to ascend rearward thatare connected to each other in the vehicle longitudinal direction. Aportion of the cutout 32 extends across the front slope surface 36. Therear slope surface 38 is a flat surface having neither a cutout nor ahole. It can be said that a rear end (i.e., an upper end) of the rearslope surface 38 is located higher than a lower end of the fasteningbolt 42 as described in detail later, and the rear slope surface 38faces the head of the fastening bolt 42 in the vehicle longitudinaldirection.

Further, as is apparent from FIGS. 3 and 5, the fastening hole 30, thecutout 32, and the recess 34 are all formed in each of the raised parts28. As shown in FIG. 5, a projection amount of the raised parts 28 fromthe recessed parts 26 is greater than a thickness of the head of thefastening bolt 42. In other words, a lower end of each of the recessedparts 26 is located lower than the lower end of the fastening bolt 42 ata position identical to the fastening bolt 42 in the longitudinaldirection. Accordingly, both sides in the vehicle width direction of thefastening bolt 42 are always surrounded by upright walls 40 extendingfrom the raised parts 28 to the recessed parts 26. This makes othermembers less prone to coming into contact with the fastening bolt 42,which in turn makes it possible to effectively prevent damage orloosening of the fastening bolt 42.

A rear portion of the protector 14 is attached directly to a bottomsurface of the battery 10 or indirectly to the bottom surface of thebattery 10 with a battery frame (not shown) or the like interposedtherebetween. The protector 14 may be attached to the battery 10 byfastening using a bolt or a rivet, or by welding. In any case, attachingthe rear portion of the protector 14 to the bottom surface of thebattery 10 allows the protector 14 to cover the connectors 18 projectingfrom the front surface of the battery 10 from below. This makes itpossible to protect the connectors 18 from contact with a road surfaceor a flipped stone.

In the meantime, in this example, such connectors 18 are disposed abovethe recessed parts 26 of the protector 14. This will be described withreference to FIG. 6. FIG. 6 is a schematic cross-sectional view takenalong a line C-C of FIG. 1. As is apparent from FIG. 6, the connectors18 are all located above the recessed parts 26. This configuration makesit possible to sufficiently secure a distance between each of theconnectors 18 and the protector 14 and accordingly prevent theconnectors 18 and the protector 14 from coming into contact with eachother. Further, such a configuration allows the protector 14 to bedisposed higher than a configuration where the connectors 18 aredisposed above the raised parts 28. As a result, the likelihood ofcontact between the protector 14 and the road surface can also bereduced.

As described above, the protector 14 is fastened to the attachment bar16. The attachment bar 16 is a member attached to a lower portion of therear cross part 22. FIG. 7 is a partial perspective view of theattachment bar 16 as viewed from below. In this example, the attachmentbar 16 is a rectangular tubular member elongated in the vehicle widthdirection. A through hole 44 used for fastening the attachment bar 16 tothe protector 14 is formed through a bottom surface of the attachmentbar 16. Further, onto a back surface side of the through hole 44, theweld nut 43 (see FIG. 5) into which the fastening bolt 42 is screwed isfixed.

A through hole 46 used for fastening the attachment bar 16 to the rearcross part 22 is formed at an end and through an upper surface of theattachment bar 16. Further, as shown in FIG. 7, the bottom surface ofthe attachment bar 16 that faces the through hole 46 is largely cut out,allowing insertion of the fastening bolt 48 from below. At a portion ofthe rear cross part 22 corresponding to the through hole 46, aninsertion hole through which the fastening bolt 48 is inserted isformed, and further, on a back surface side of the insertion hole, aweld nut 50 into which the fastening bolt 48 is screwed is fixed.However, the attachment of the attachment bar 16 to the rear cross part22 described here is an example, and both the attachment bar 16 and therear cross part 22 may be attached to each other by a different methodsuch as welding.

Here, as described above and shown in FIG. 5, the rear cross part 22 hasan arch shape whose center in the vehicle width direction is convex. Theattachment bar 16 is attached to a bottom surface of the rear cross part22 so as to extend across the arch. This produces a certain gap betweenthe upper surface of the attachment bar 16 and the bottom surface of therear cross part 22 at the center in the vehicle width direction.

As shown in FIG. 2, the attachment bar 16 may have a position and sizesuch that a lower end of the attachment bar 16 is located lower than thelower ends of the connectors 18 and higher than the lower end of thebattery 10. This configuration makes it possible to effectively preventthe protector 14 from coming into contact with an object dropped on aroad (hereinafter referred to as an “on-road dropped object”). This willbe described later.

Next, the reason why the protector 14 and the attachment bar 16 asdescribed above are provided will be described. FIGS. 8 to 10 areschematic side views of a section around the battery 10 and the rearcross part 22. FIG. 8 shows a configuration where neither the protector14 nor the attachment bar 16 is provided, FIG. 9 shows a configurationwhere only the protector 14 is provided but the attachment bar 16 is notprovided, and FIG. 10 shows a configuration where both the protector 14and the attachment bar 16 are provided.

Various objects (on-road dropped objects 100) are dropped on a road, andsome of the on-road dropped objects 100 are relatively large. When thelower end of the rear cross part 22 is located higher than the lowerends of the connectors 18, some of such on-road dropped objects 100 maycollide with the connectors 18. For example, as shown in FIG. 8, it isassumed that an on-road dropped object 100 lower than the lower end ofthe rear cross part 22 but higher than the lower ends of the connectors18 is dropped on a road. In this case, the on-road dropped object 100passes under the rear cross part 22 and collides with the connectors 18as the vehicle travels, which may damage or deteriorate the connectors18.

On the other hand, as shown in FIG. 9, it is assumed that the protector14 that covers and protects the connectors 18 from below is laid betweenthe rear cross part 22 and the battery 10. In this case, as in FIG. 8,even when the on-road dropped object 100 is present, the on-road droppedobject 100 collides with the protector 14 before colliding with theconnectors 18. Then, the collision of the on-road dropped object 100with the protector 14 causes the vehicle to move upward to run over theon-road dropped object 100, thereby preventing the connectors 18 fromcolliding with the on-road dropped object 100.

However, since the protector 14 is a thin plate, the protector 14 may bedeformed or damaged when colliding with the on-road dropped object 100with a strong force. In this example, as described above and shown inFIG. 10, the attachment bar 16 is interposed between the protector 14and the rear cross part 22. The attachment bar 16 extends across thearch formed by the rear cross part 22. In other words, the attachmentbar 16 is attached to a position sufficiently lower than the center inthe vehicle width direction of the rear cross part 22. Accordingly, manyof the on-road dropped objects 100 collide with the attachment bar 16before colliding with the protector 14 as the vehicle travels. When theon-road dropped object 100 collides with the attachment bar 16, thevehicle moves upward to run over the on-road dropped object 100. As aresult, the contact between the on-road dropped object 100 and theprotector 14 is suppressed, which in turn effectively preventsdeformation or damaged of the protector 14.

In general, the larger an angle between a direction of the force appliedto the protector 14 and the surface of the protector 14, the more theprotector 14 is prone to being deformed, and the more the direction ofthe force becomes parallel to the surface of the protector 14, the lessthe protector 14 is prone to being deformed. When the attachment bar 16is interposed between the protector 14 and the rear cross part 22, theheight of the front end of the protector 14 is lowered, and theinclination of the protector 14 becomes gentle. That is, an attachmentposture of the protector 14 becomes almost level. Accordingly, even whenthe on-road dropped object 100 collides with the protector 14, the anglebetween the direction of the force applied at the collision (generally,parallel to the road surface) and the protector 14 is small. As aresult, even when the on-road dropped object 100 collides with theprotector 14, the protector 14 is less prone to being deformed.

Here, in order for the on-road dropped object 100 to pass under thelower end of the attachment bar 16 to avoid colliding with the protector14 and the connectors 18, the lower end of the attachment bar 16 may belowered to some degree. However, when the lower end of the attachmentbar 16 is excessively lowered, contact between the attachment bar 16 andthe road surface frequently occurs. Therefore, in this example, theattachment bar 16 has a position and size such that the lower end of theattachment bar 16 is located lower than the lower ends of the connectors18 and higher than the lower end of the battery 10. Such a position andsize makes it possible to prevent the on-road dropped object 100 fromcoming into contact with the protector 14 while suppressing contactbetween the attachment bar 16 and the road surface.

In the meantime, in the front collision where an obstacle collides withthe front of the vehicle, a large force (collision load) directedrearward of the vehicle is produced in the suspension member 12. Whenthe battery 10 and the suspension member 12 are connected by theprotector 14, the collision load is transmitted to the front portion ofthe battery 10. The rear portion of the battery 10 is rigidly fixed to abody or frame, so when such a collision load is transmitted to the frontportion of the battery 10, a compressive stress in the vehiclelongitudinal direction is undesirably produced in the battery 10.

Therefore, in this example, in order for the protector 14 and thesuspension member 12 to easily disconnect from each other in the frontcollision, the cutout 32 is provided adjacent to the rear side of thefastening hole 30 and connected to the fastening hole 30. Further, inthis example, as described above, the rear slope surface 38 inclined toascend rearward is further provided adjacent to the rear side of thefastening hole 30. An effect of the cutout 32 and the rear slope surface38 will be described with reference to FIGS. 11 and 12. FIGS. 11 and 12are schematic cross-sectional views of a section around the fasteninghole 30, FIG. 11 shows a normal state, and FIG. 12 shows a state in thefront collision.

Since the cutout 32 is connected to the rear side of the fastening hole30, as shown in FIG. 12, the fastening bolt 42 can easily move rearwardof the vehicle. Accordingly, when the suspension member 12 and theattachment bar 16 fixed to the suspension member 12 move rearward at thefront collision, the fastening bolt 42 also moves rearward of thevehicle and passes through the cutout 32. This causes the protector 14and the attachment bar 16; that is, the protector 14 and the suspensionmember 12, to disconnect from each other to prevent transmission of theload to the front portion of the battery 10.

Here, in this example, the rear slope surface 38 inclined to ascendrearward is provided adjacent to a rear side of the cutout 32. When thefastening bolt 42 passes through the cutout 32 and moves rearward, thehead of the fastening bolt 42 collides with the rear slope surface 38. Aforce produced by this collision is converted to a forward and downwardforce by the rear slope surface 38 inclined to ascend rearward to causethe protector 14 to easily move downward. Then, when the protector 14moves downward, load transmission to the battery 10 through theprotector 14 is more reliably prevented.

Note that, in order to cause the fastening bolt 42 to collide with therear slope surface 38, the upper end of the rear slope surface 38 needsto be located higher than the lower end of the fastening bolt 42.Generally, the steeper the inclination angle of the protector 14, thelower the location of the upper end of the rear slope surface 38. Inthis example, interposing the attachment bar 16 between the protector 14and the suspension member 12 makes the protector 14 almost level. Thus,a difference in height between the upper end of the rear slope surface38 and the fastening hole 30 can be suppressed, and the fastening bolt42 can be made to collide with the rear slope surface 38 more reliably.

Note that the above description is an example, and as long as at leastthe protector 14 laid between the battery 10 and the suspension member12 is provided, the remaining configuration may be changed asappropriate. For example, although in this example the cutout 32 and therecess 34 that are connected to the fastening hole 30 are provided inthe protector 14, any of them is not necessarily provided. Further, theprotector 14 and the attachment bar 16 may be attached to each other bynot only fastening using a bolt, but also other connections such asfastening using a rivet or welding.

Further, the position, size, and shape of the attachment bar 16 may bechanged as appropriate. Thus, for example, the attachment bar 16 mayhave a shape other than the rectangular tubular shape. For example, theattachment bar 16 may have a substantially hat shape having a plateelongated in the vehicle width direction and legs having a substantiallyL-shape that extend upward from both ends of the plate for fastening tothe rear cross part 22. Further, the protector 14 may be directlyconnected to the suspension member 12 without the attachment bar 16.Further, the shape of the protector 14 may also be changed asappropriate, and may be, for example, a flat shape without any of therecessed part 26, the raised part 28, and the recess 34, or may becurved as a whole.

1. A vehicle underfloor structure comprising: a battery disposed under afloor of a vehicle and having at least one connector projecting from afront end of the battery; a suspension member provided adjacent to avehicle front side of the battery, a lower end of the suspension memberbeing located higher than a lower end of the battery; and a protectorcovering and protecting the at least one connector from below, theprotector being laid between the battery and the suspension member. 2.The vehicle underfloor structure according to claim 1, furthercomprising an attachment bar attached to a lower portion of thesuspension member and extending in a vehicle width direction, wherein afront portion of the protector is attached to the attachment bar.
 3. Thevehicle underfloor structure according to claim 2, wherein a lower endof the attachment bar is located lower than a lower end of the at leastone connector and higher than the lower end of the battery.
 4. Thevehicle underfloor structure according to claim 2, wherein at a rearportion of the suspension member, a rear cross part is provided, therear cross part having an arch shape, extending in the vehicle widthdirection, and having a center in the vehicle width direction convex,and the attachment bar is attached to the rear cross part to extendacross the arch.
 5. The vehicle underfloor structure according to claim3, wherein at a rear portion of the suspension member, a rear cross partis provided, the rear cross part having an arch shape, extending in thevehicle width direction, and having a center in the vehicle widthdirection convex, and the attachment bar is attached to the rear crosspart to extend across the arch.